In the early stage of shale gas well development, the production is high and most of the wells are directly put into production with hollow casing, which can effectively enhance production with liquid. Under the production system of releasing pressure, the wellhead pressure quickly drops to transmission pressure, and then there are abnormal production with liquid, wellbore liquid accumulates, production shutdown by floods, which causes dramatic drop to the life cycle of gas wells. For this purpose, it is necessary to lower the production string and implement the follow-up drainage and gas recovery process. No clear string lowering technology has been developed to guide field production in the early stage, so it is impossible to promote the implementation in a systematic and efficient manner under a scientific and reasonable plan when shale gas production is on a large scale. Based on the characteristics of shale gas wells production in late stage, such as low pressure, long horizontal section, etc., through the analysis on maximum gas production, wellbore pressure loss, gas erosion resistance calculation, wellbore flow law, liquid carrying capacity, and assisting drainage & gas recovery in late stage, combined with a large number of field application analysis, technical requirements are put forward for optimizing string such as lowering timing, tubing size, string structure and lowering depth, etc. The application results show that this technology can effectively reduce the decline rate of gas wells and provide a technical basis for the timely implementation of subsequent drainage & gas recovery measures and maintenance of gas well productivity.